import { useEffect, useMemo, useState } from 'react';
import type { DemoLocale } from './types';

type InvoiceScene = {
  id: 'source' | 'ocr' | 'fields';
  durationMs: number;
};

type InvoiceFeatureDemoProps = {
  locale: DemoLocale;
  isBusy: boolean;
};

const COPY = {
  en: {
    title: 'Invoice Demo',
    busy: 'Running',
    hidden: 'Hidden',
    play: 'Play',
    pause: 'Pause',
    replay: 'Replay',
    hide: 'Hide',
    show: 'Show',
    videoName: 'invoice_demo.webm',
    step: 'Step',
    lanes: {
      source: 'Source',
      ocr: 'OCR',
      fields: 'Fields',
    },
    captions: {
      source: 'Upload and validate invoice source',
      ocr: 'Extract raw text and parse blocks',
      fields: 'Return structured invoice fields',
    },
    words: {
      source: ['File', 'Role', 'Note'],
      ocr: ['Read', 'Parse', 'Check'],
      fields: ['Total', 'Due', 'Status'],
      streamWords: ['Reading', 'Parsing', 'Checking', 'Packing'],
      sourceImage: 'https://upload.wikimedia.org/wikipedia/commons/9/90/Standard_Fapiao.jpg',
    },
  },
  'zh-TW': {
    title: '發票導覽',
    busy: '執行中',
    hidden: '已隱藏',
    play: '播放',
    pause: '暫停',
    replay: '重播',
    hide: '隱藏',
    show: '顯示',
    videoName: '發票導覽影片.webm',
    step: '步驟',
    lanes: {
      source: '來源',
      ocr: '辨識',
      fields: '欄位',
    },
    captions: {
      source: '上傳並驗證發票來源',
      ocr: '擷取原文並解析區塊',
      fields: '輸出結構化發票欄位',
    },
    words: {
      source: ['檔案', '角色', '備註'],
      ocr: ['讀取', '解析', '驗證'],
      fields: ['總額', '到期', '狀態'],
      streamWords: ['讀取中', '解析中', '驗證中', '封裝中'],
      sourceImage: 'https://upload.wikimedia.org/wikipedia/commons/9/90/Standard_Fapiao.jpg',
    },
  },
} as const;

const SCENES: InvoiceScene[] = [
  { id: 'source', durationMs: 1650 },
  { id: 'ocr', durationMs: 1750 },
  { id: 'fields', durationMs: 1700 },
];

export default function InvoiceFeatureDemo({ locale, isBusy }: InvoiceFeatureDemoProps) {
  const copy = COPY[locale];
  const scenes = useMemo(() => SCENES, []);

  const [sceneIndex, setSceneIndex] = useState(0);
  const [elapsedMs, setElapsedMs] = useState(0);
  const [isPlaying, setIsPlaying] = useState(true);
  const [isCollapsed, setIsCollapsed] = useState(false);
  const [reducedMotion, setReducedMotion] = useState(false);

  useEffect(() => {
    const media = window.matchMedia('(prefers-reduced-motion: reduce)');
    const apply = () => setReducedMotion(media.matches);
    apply();
    if (media.addEventListener) {
      media.addEventListener('change', apply);
      return () => media.removeEventListener('change', apply);
    }
    media.addListener(apply);
    return () => media.removeListener(apply);
  }, []);

  useEffect(() => {
    if (reducedMotion) setIsPlaying(false);
  }, [reducedMotion]);

  useEffect(() => {
    setSceneIndex(0);
    setElapsedMs(0);
    setIsCollapsed(false);
    if (!reducedMotion) setIsPlaying(true);
  }, [locale, reducedMotion]);

  useEffect(() => {
    if (!isBusy) return;
    setIsCollapsed(true);
    setIsPlaying(false);
  }, [isBusy]);

  useEffect(() => {
    if (!isPlaying || isCollapsed || isBusy || reducedMotion) return;
    const timer = window.setInterval(() => {
      setElapsedMs((prev) => {
        const scene = scenes[sceneIndex];
        if (!scene) return 0;
        const next = prev + 120;
        if (next < scene.durationMs) return next;
        setSceneIndex((current) => (current + 1) % scenes.length);
        return 0;
      });
    }, 120);
    return () => window.clearInterval(timer);
  }, [isPlaying, isCollapsed, isBusy, reducedMotion, scenes, sceneIndex]);

  const activeScene = scenes[sceneIndex] ?? scenes[0];
  const totalDuration = scenes.reduce((sum, scene) => sum + scene.durationMs, 0);
  const previousDuration = scenes.slice(0, sceneIndex).reduce((sum, scene) => sum + scene.durationMs, 0);
  const progress = totalDuration > 0 ? Math.round(((previousDuration + elapsedMs) / totalDuration) * 100) : 0;
  const sceneCaption = copy.captions[activeScene.id];
  const streamOffset = Math.floor(elapsedMs / 420);
  const activeStreamWords = copy.words.streamWords.map(
    (_word, index) => copy.words.streamWords[(streamOffset + index) % copy.words.streamWords.length]
  );

  const replay = () => {
    setSceneIndex(0);
    setElapsedMs(0);
    if (!reducedMotion && !isBusy) setIsPlaying(true);
  };

  if (isCollapsed) {
    return (
      <section className="invoice-walk-collapsed" aria-live="polite">
        <div className="invoice-walk-mini-markers" aria-hidden="true">
          <span />
          <span />
          <span />
        </div>
        <p>{isBusy ? copy.busy : copy.hidden}</p>
        {!isBusy ? (
          <button
            type="button"
            className="ghost-btn"
            onClick={() => {
              setIsCollapsed(false);
              replay();
            }}
          >
            {copy.show}
          </button>
        ) : null}
      </section>
    );
  }

  return (
    <section className="invoice-walk-video" aria-label={copy.title}>
      <header className="invoice-walk-head">
        <div>
          <h3>{copy.title}</h3>
          <small>
            {copy.step} {sceneIndex + 1}/{scenes.length}
          </small>
        </div>
        <div className="invoice-walk-actions">
          <button
            type="button"
            className="invoice-walk-icon-btn"
            onClick={() => setIsPlaying((prev) => !prev)}
            disabled={isBusy || reducedMotion}
            aria-label={isPlaying ? copy.pause : copy.play}
          >
            {isPlaying ? '||' : '>'}
          </button>
          <button type="button" className="invoice-walk-icon-btn" onClick={replay} disabled={isBusy} aria-label={copy.replay}>
            R
          </button>
          <button type="button" className="invoice-walk-icon-btn" onClick={() => setIsCollapsed(true)} aria-label={copy.hide}>
            X
          </button>
        </div>
      </header>

      <div className="invoice-walk-frame" data-scene={activeScene.id}>
        <div className="invoice-walk-windowbar">
          <span />
          <span />
          <span />
          <small>{copy.videoName}</small>
        </div>

        <div className="invoice-walk-canvas">
          <section className="invoice-walk-lane source">
            <span className="invoice-walk-lane-index">1</span>
            <small className="invoice-walk-lane-label">{copy.lanes.source}</small>
            <div className="invoice-walk-chip-row">
              {copy.words.source.map((item) => (
                <span key={item}>{item}</span>
              ))}
            </div>
            <div className="invoice-walk-dropzone">
              <img
                src={copy.words.sourceImage}
                alt={locale === 'zh-TW' ? '發票樣本' : 'invoice sample'}
                loading="lazy"
                referrerPolicy="no-referrer"
              />
              <p>{locale === 'zh-TW' ? 'invoice_sample.jpg' : 'invoice_sample.jpg'}</p>
            </div>
          </section>

          <section className="invoice-walk-lane ocr">
            <span className="invoice-walk-lane-index">2</span>
            <small className="invoice-walk-lane-label">{copy.lanes.ocr}</small>
            <div className="invoice-walk-ocr-nodes">
              {copy.words.ocr.map((item) => (
                <span key={item}>{item}</span>
              ))}
            </div>
            <div className="invoice-walk-ocr-flow">
              <span />
            </div>
            <div className="invoice-walk-ocr-lines">
              {activeStreamWords.slice(0, 3).map((word, index) => (
                <div key={`${word}-${index}`} className={`invoice-walk-stream-pill ${index === 0 ? 'lg' : index === 1 ? 'md' : 'sm'}`}>
                  <span>{word}</span>
                </div>
              ))}
            </div>
          </section>

          <section className="invoice-walk-lane fields">
            <span className="invoice-walk-lane-index">3</span>
            <small className="invoice-walk-lane-label">{copy.lanes.fields}</small>
            <div className="invoice-walk-field-grid">
              {copy.words.fields.map((item) => (
                <article key={item}>
                  <small>{item}</small>
                  <strong>{item === copy.words.fields[0] ? 'NT$ 6,665' : item === copy.words.fields[1] ? '2026-03-31' : locale === 'zh-TW' ? '草稿' : 'Draft'}</strong>
                </article>
              ))}
            </div>
            <p>{locale === 'zh-TW' ? '已產生 JSON 與可讀預覽。' : 'JSON payload and readable preview generated.'}</p>
          </section>
        </div>
      </div>

      <footer className="invoice-walk-meta">
        <div className="invoice-walk-progress-track" aria-hidden="true">
          <span style={{ width: `${Math.min(100, Math.max(0, progress))}%` }} />
        </div>
        <p className="invoice-walk-caption">{sceneCaption}</p>
        <div className="invoice-walk-scene-dots">
          {scenes.map((scene, index) => (
            <button
              key={scene.id}
              type="button"
              className={`invoice-walk-scene-dot ${index === sceneIndex ? 'active' : index < sceneIndex ? 'complete' : ''}`}
              onClick={() => {
                setSceneIndex(index);
                setElapsedMs(0);
              }}
              aria-label={`${copy.step} ${index + 1}`}
            >
              <span />
            </button>
          ))}
        </div>
      </footer>
    </section>
  );
}